This invention relates to improved flail feedout means for mowing and trimming devices used to trim grass, weeds, and other vegetation, of the rotary type equipped with flexible cord-like flails formed of generally cylindrical fibers. Grass and weed cutters of this general type are now widely used. Examples are described in REBER, U.S. Pat. No. 3,664,102; BALLAS et al, U.S. Pat. No. 3,826,068; MIZUNO et al, U.S. Pat. No. 4,020,552; BALLAS et al, U.S Pat. No. 4,035,912; PROULX, U.S. Pat. No. 4,097,991; PERDUE, U.S. Pat. No. 4,134,204; TORO, Belgium Patent No. 852,150; PROULX, U.S. Pat. No. 4,145,809; PROULX, U.S. Pat. No. 4,203,212; and PROULX, U.S. Pat. No. 4,259,782.
Such devices are available on the market having automatic flail feedout mechanisms which respond to a bump on the ground intentionally applied by the operator or by application of force applied thereto by some mechanical arrangement. Such mechanisms usually consist of a dog or friction clutch located between a spool of flail and the case thereabout through which the flail is fed. By bumping an extension of the spool on the ground, the friction clutch is disengaged for a length of time dependent on the duration of the bump. The dog clutch released by the bump then abruptly engages at the next opportunity to feed out flail in segment lengths which are related to the engagement points of the dog clutch. Such dog clutches have outwardly extending ribs which engage inwardly extending abutment tangs and therefore depend upon a skillful bump when it is desired that they deliver only one segment length. However, friction within the device and over zealous bumping can result in two or more line segments being fed out, especially when the device has been in use and the corners on the ribs and tangs have worn so that positive engagement is no longer assured. The unavoidable abrupt operation of the dog clutch causes the wear to take place. Therefore, there has been need for a feedout mechanism which automatically feeds out a predetermined length of flail per bump, which does not lose this capability with extended use, and which is easy to construct and maintain.
Other mowers such as are shown in Applicant's U.S. Pat. Nos. 4,203,212 and 4,259,782 include flail feedout means. These means have a downwardly projecting bumper as part of the flail spool which normally is used to space the flail above the surface in the plane in which the vegetation is cut. This spool, bumper and an intermediate member, as an assembly, are spring loaded downwardly with respect to the spinning housing. Extending inwardly from the intermediate cylinder are tangs which ride in a serpentinous cam slot in a cam member fixed to the housing. When the bumper is bumped on the ground, the intermediate cylinder is moved upwardly so that its tangs ride up relatively vertical cam surfaces until they reach spiral surfaces which extend downwardly to the next vertical cam surface. The net effect is that the spool connected to the intermediate members and the housing connected to the cam member rotate relative to each other to allow a predetermined length of flail to feed out by centrifugal force. This system works well, but the serpentinous cam is not as economical to manufacture as is desired and the tangs, no matter how they are multiplied, can only present a limited contact area for engagement to the serpentinous cam.
In U.S. Pat. No. 4,458,419, a pair of disc-shaped cams are radially mounted on the centerline of the cutter oriented at 45.degree. to each other. They interact with a single cam follower so that when a first cam is moved axially out of contact with the follower, by bumping of the rotating body on the ground, the other moves axially into engagement with the follower after a 45.degree. rotation. Once the bump is over, the second cam moves axially in the reverse direction, disengaging the cam follower and allowing another 45.degree. of rotation before the first cam, repositioned by the axial movement comes into abutment contact with the cam follower. The 90.degree. rotation allows a predetermined length of flail to be fed out through the body of the device. Unfortunately, some of the parts of the mechanism of the 4,458,419 patent are relatively complex to mold and tabs forming part of the follower assembly can fail after prolonged abuse.
Therefore, there has been a need for a flail feedout mechanism which operates as effectively and reliably as those shown in U.S. Pat. Nos. 4,259,782 and 4,458,419, which can be manufactured at a lower cost, and which is even more reliable in service.